// Functions and Methods in JavaScript

// 1. Functions in JavaScript

// 1.1. What is a Function?

// A function in JavaScript is a reusable block of code that performs a specific task.

// Functions help with code reuse, modularity, and abstraction by breaking code into

// manageable parts, enabling you to focus on the function's behavior rather than implementation.

// Functions take inputs (parameters), process them, and return an output.

// 1.2. Defining a Function

// Functions are defined using the `function` keyword followed by the function name,

// parameters (optional), and a block of code.

// Syntax:

function functionName(parameter1, parameter2) {

// code to be executed

}

// Example:

function greet(name) {

return "Hello, " + name + "!";

}

// Usage:

let greeting = greet("John");

console.log(greeting); // Output: Hello, John!

// 1.3. Function Execution

// A function must be invoked (or called) to execute its code. You invoke a function by

// writing its name followed by parentheses (). If the function has parameters,

// you pass arguments inside the parentheses.

greet("Alice"); // Function call

// 1.4. Functions with Default Parameters

// JavaScript allows functions to have default parameter values.

// If a function is called without an argument, the default value is used.

function multiply(a, b = 1) {

return a * b;

}

console.log(multiply(5)); // Output: 5 (since b defaults to 1)

console.log(multiply(5, 3)); // Output: 15

// 1.5. Anonymous Functions

// An anonymous function is a function without a name. They are commonly used

// as arguments to other functions or as immediate expressions,

// like in event handlers or callback functions.

let multiplyAnonymous = function(a, b) {

return a * b;

};

console.log(multiplyAnonymous(4, 5)); // Output: 20

// 1.6. Arrow Functions

// Arrow functions, introduced in ES6, are a shorter syntax for writing functions.

// They are anonymous and omit the `function` keyword. Arrow functions are useful

// for writing short, concise functions, particularly callback functions.

const greetArrow = (name) => "Hello, " + name + "!";

console.log(greetArrow("Alice")); // Output: Hello, Alice!